Combustion by-pass for back-drafting blast furnaces



Dec. 1, 1964 A R. J. FLANAGAN 3,

COMBUSTION BY-PASS FOR BACK-DRAFTING BLAST FURNACES Filed June 3, 1963 LCombustion A ir INVENTOI? RQBERT J. FLA/VAGAN i /1e: W

mm m ey United States Patent F 3 159 385 (JOMBUSTION BY-PASS FORBACK-DRAFTKNG BLAST FURNACES Robert J. Flanagan, McKeesport, Pa.,assignor to United States Steel Corporation, a corporation of New JerseyFiled June 3, 1963, Ser. No. 285,061 4 Claims. (Cl. 263-19) Thisinvention relates to a by-pass for back-drafting blast furnaces and, inparticular, to a valved combustionchamber by-pass extending from a pointon the hot-blast main adjacent the furnace, to the chimney main.

The need for back-drafting blast furnaces and the objections to theconventional method of so doing are explained in Heist et al. Patent1,879,230, which discloses an elemental by-pass for the purpose. Myinvention is an improvement thereon in that I provide a combustionchamber wherein the combustible gases withdrawn from the furnace may besafely burned. I also provide the chamber with a supply of air forcombustion and with temperature-control means to prevent excessive heatfrom resulting which might damage the lining of the chimney main andchimney.

A complete understanding of the invention may be obtained from thefollowing detailed description and explanation which refer to theaccompanying drawing illustrating the present preferred embodiment, thesingle figure of which is a diagrammatic layout showing the arrangementin plan of the air-preheating system of a blast furnace, incorporatingmy invention.

Referring now in detail to the drawing, the bustle pipe of ablast-furnace (not shown) receives preheated air from hot-blast main 11.The .air is heated in one of stoves 12, 13 and 14 adapted to beconnected to the main by hot-blast valves 15. Air \at atmospherictemperature is supplied to the stoves from a cold-blast main 16 underthe control of cold-blast valves 17. According to the usual practice,two of the three stoves are on gas, i.e., being fired with blast-furnacegas, while the other is on blast. The stoves on gas have their valvesand 17 closed and the products of combustion therein flow to a chimneymain 18 through chimney valves 19 which are open. The chimney valves ofthe stove on blast are closed but its valves 15 and 17 are open. Chimneymain 18 extends to chimney 20.

The system described thus far is conventional. My improvement thereinconsists in the provision of a combustion by-pass 21 extending from apoint in the hot-blast main 11 adjacent bustle pipe 10 to the chimneymain 18, conveniently the end thereof remote from chimney 20. Theby-pass includes a normally closed valve 22 controlling the flow ofgases therein.

In greater detail, the by-pass 21 comprises principally arefractory-lined elongated combustion chamber 23 into the frusto-conicalentering end of which a refractory-lined inlet pipe 24 from main 11extends as an inspirator, whereby air for combustion is drawn in througha lateral airsupply pipe 25 having a valve 26 therein. From the otherend of chamber 23, a refractory-lined exit pipe 27, in spaced relationthereto, extends to main 18.

A wind box 28 surrounds the adjacent but spaced ends of chamber 23 andpipe 27, land the inlet pipe 29 thereof has a control valve 30 therein.Air admitted through pipe 29 tempers combustion products formed inchamber 3,15,385 Patented Dec. 1,, 1964 23 and reduces their temperatureto a value such that they will not damage the lining of pipe 27 or main13.

Chamber 23 is provided at the end adjacent pipe 25 with an ignitor 31. Athermostat 32 in pipe 27 is connected to a controller 33 whichautomatically adjusts valve 30 to maintain the temperature of the exitgases below a predetermined maximum.

When it is desired to back draft the furnace, the stove on blast istaken off by closing its valves 15 and 17, placing it in a so-calledbottled condition. Valve 22 which is normally closed is opened and thedraft of chimney 2t) withdraws residual gases from the furnace, creatinga condition of negative pressure therein. These gases are combustibleand, on reaching chamber 23 are fired by ignitor or hot tube 31 of knownconstruction, in the presence of combustion air admitted by openingvalve 26. The combustion products pass on to pipe 27 but have theirtemperature reduced to a safe value by cooling air from wind box 28before entry into the pipe.

When the desired period of back-drafting has elapsed, normal operationmay be resumed by a reversal of the operations just described.

It will be evident that my invention provides a backdnafting by-pass inthe form of a combustion chamber with means for admitting a controlledamount of combustion air and cooling air in the amount necessary toprevent the temperature of the combustion products going to the chimneyfrom exceeding a predetermined value. More particularly, the inventionprovides a valved combustion bypass from a point on the hot-blast Inain11 adjacent the furnace to the chimney main 18.

Although I have disclosed herein the preferred embodiment of myinvention, I intend to cover as well any change or modification thereinwhich may be made Without departing from the spirit and scope of theinvention.

I claim:

1. The combination with a blast furnace bustle pipe, a plurality ofstoves thereadjacent and cold-blast, hot-blast and chimney mainsconnected to said stoves, of a combustion by-pass comprising an inletpipe connected to said hot-bl ast main at a point adjacent the bustlepipe, an exit pipe connected to said chimney main, an elongatedcombustion chamber connected between said inlet and exit pipes, and acombustion-air supply pipe connected to said chamber.

2. The combination defined in claim 1, characterized by said chamberhaving a frusto-conical entrance end into which said inlet pipe extendsin spaced relation.

3. The combination defined in claim 1, characterized by a cooling-airsupply pipe communicating with said exit P P 4. The combination definedin claim 3, characterized by a valve in said cooling-air supply pipe, acontroller for said valve and a thermostat in said exit pipe downstreamfrom said cooling-air supply pipe, connected to said controller.

References Cited in the file of this patent UNITED STATES PATENTS803,284 Hartman et a1 Oct. 31, 1905 1,879,230 Heist et a1 Sept. 27, 19322,931,635 Braun et a1. Apr. 5, 196.0

1. THE COMBINATION WITH A BLAST FURNACE BUSTLE PIPE, A PLURALITY OFSTOVES THEREADJACENT AND COLD-BLAST, HOT-BLAST AND CHIMNEY MAINSCONNECTED TO SAID STOVES, OF A COMBUSTION BY-PASS COMPRISING AN INLETPIPE CONNECTED TO SAID HOT-BLAST MAIN AT A POINT ADJACENT THE BUSTLEPIPE, AN EXIT PIPE CONNECTED TO SAID CHIMNEY MAIN, AN ELONGATED